A plan by the immigration minister, Scott Morrison, to issue asylum seekers with temporary visas could be thrown into disarray if a move by Greens senator Sarah Hanson-Young to disallow a key regulation succeeds.

“The temporary humanitarian concern visa can be valid for up to three years. Your visa may be for a shorter amount of time as your circumstances are assessed on a case-by-case basis,“ the document said.

“If you are found to still need Australia’s protection you will be granted another temporary visa. As you arrived illegally you cannot apply for a permanent visa. If you are found to no longer be in need of Australia’s protection, you are expected to return home.”

A number of asylum seekers who are represented by refugee legal aid organisations have received invitations.